Adaptive Power Modulation

ABSTRACT

Systems and methods comprise determining a received signal strength (RSSI) of a signal. A sensitivity level of a receiver is determined, where the signal is to be received at the receiver. When a determination is made that the RSSI is greater than the sensitivity level, a transmitter power level is calculated as a difference between the RSSI and the sensitivity level. A transmitter of the signal is controlled in accordance with the transmitter power level.

RELATED APPLICATION

This application claims the benefit of U.S. Patent Application No.61/788,715, filed Mar. 15, 2013.

TECHNICAL FIELD

Embodiments described herein relate generally to systems and methods forpower modulation and, more particularly, to adaptive power modulation tooptimize battery life.

BACKGROUND

There are numerous conventional battery powered wireless devicesavailable, and these devices have a fixed transmit power and includebatteries typically sized for a year or two of operation. Thesebatteries, for example, include small lithium batteries, such as theCR2, CR123 or CR2032 coin cell batteries. Since transmit power candegrade as battery capacity diminishes, the effective range of thewireless link is also affected. As such, the device is effectively deadwhen the range of the device is adversely affected by the battery life,even through there is capacity remaining in the battery. In a securitysystem, any degradation of the system can leave the system in avulnerable state, such as a particular zone may now be unable to detectan intrusion. Thus, there is a need for adaptive power modulation tooptimize battery life in host systems.

INCORPORATION BY REFERENCE

Each patent, patent application, and/or publication mentioned in thisspecification is herein incorporated by reference in its entirety to thesame extent as if each individual patent, patent application, and/orpublication was specifically and individually indicated to beincorporated by reference.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a flow diagram of adaptive power modulation, under anembodiment.

DETAILED DESCRIPTION

Although the detailed description herein contains many specifics for thepurposes of illustration, anyone of ordinary skill in the art willappreciate that many variations and alterations to the following detailsare within the scope of the embodiments described herein. Thus, thefollowing illustrative embodiments are set forth without any loss ofgenerality to, and without imposing limitations upon, the claimedinvention.

FIG. 1 is a flow diagram of adaptive power modulation 100, under anembodiment. Systems and methods comprise determining a received signalstrength (RSSI) of a signal 102. A sensitivity level of a receiver isdetermined 104, where the signal is to be received at the receiver. Whena determination is made that the RSSI is greater than the sensitivitylevel, a transmitter power level is calculated as a difference betweenthe RSSI and the sensitivity level 106. A transmitter of the signal iscontrolled in accordance with the transmitter power level 108.

Wireless range is given by the Friis' equation asP _(r) =P _(t) *G _(t) *G _(r)*losswhere the variable P_(t) represents transmit power, the variable P_(r)represents receiver power, the variable G_(r) represents receiverantenna gain, and the variable G_(t) represents transmitter antennagain. Assuming a fixed range for any given wireless sensor (i.e., thesensor is fixed in space, and not moving), then some sensors will havemore than adequate receive power. For example, a device has 100 mWtransmit power (20 dBm), the antenna gains are both 2 dBi, receiversensitivity is −100 dBm and the distance is 20 m. To accommodate humanbody absorption, the example allows 15 dBm as margin in the system. Thismeans the minimum RSSI for the link should be approximately equivalentto the receiver sensitivity adjusted for the absorption (e.g., −85 dBm).If the sensor is placed only 10 m away, then the receiver is seeing muchmore power than required to obtain and recover the communications. Thismeans current being used by the power amplifier (PA) and low noiseamplifier (LNA) is being wasted, thus also wasting battery life.

Upon sensor pairing, i.e. a method of connecting two wireless devices,say as used in Zigbee communication protocol, the two devicescommunicate on each packet, both the received signal strength (RSSI) ofthe other devices(s) in the communication system. If the RSSI is greaterthan the sensitivity level (e.g., −80 dBm (allowing approximately 5 dBmfor signal to noise ratio)), then the difference between the RSSIreceived and the sensitivity level (e.g., −80 dBm) is the amount ofpower being wasted for that link. So the amount of power reduction usingthe adaptive power modulation of an embodiment, and thus amount ofbattery capacity that can be saved, is the difference, on apacket-to-packet basis, between the RSSI and the sensitivity level(e.g., −80 dBm).

Therefore, using the example described herein, if the RSSI is −60 dBm,then the amount of power difference is 20 dBm. If that transmitter isoriginally putting out 20 dBm, it could be reduced to 0 dBm to achievethe same communication link range for that particular sensor and saveapproximately 99 mW of power.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,” and thelike are to be construed in an inclusive sense as opposed to anexclusive or exhaustive sense; that is to say, in a sense of “including,but not limited to.” Words using the singular or plural number alsoinclude the plural or singular number respectively. Additionally, thewords “herein,” “hereunder,” “above,” “below,” and words of similarimport, when used in this application, refer to this application as awhole and not to any particular portions of this application. When theword “or” is used in reference to a list of two or more items, that wordcovers all of the following interpretations of the word: any of theitems in the list, all of the items in the list and any combination ofthe items in the list.

The above description of embodiments and corresponding systems andmethods is not intended to be exhaustive or to limit the systems andmethods to the precise forms disclosed. While specific embodiments of,and examples for, the systems and methods are described herein forillustrative purposes, various equivalent modifications are possiblewithin the scope of the systems and methods, as those skilled in therelevant art will recognize. The teachings of the systems and methodsprovided herein can be applied to other systems and methods, not onlyfor the systems and methods described above.

The elements and acts of the various embodiments described above can becombined to provide further embodiments. These and other changes can bemade to the embodiments and corresponding systems and methods in lightof the above detailed description.

In general, in the following claims, the terms used should not beconstrued to limit the invention and corresponding systems and methodsto the specific embodiments disclosed in the specification and theclaims, but should be construed to include all systems that operateunder the claims. Accordingly, the invention and corresponding systemsand methods is not limited by the disclosure, but instead the scope isto be determined entirely by the claims.

While certain aspects of the systems and methods are presented below incertain claim forms, the inventors contemplate the various aspects ofthe systems and methods in any number of claim forms. Accordingly, theinventors reserve the right to add additional claims after filing theapplication to pursue such additional claim forms for other aspects ofthe systems and methods described herein.

What is claimed is:
 1. A method comprising: receiving, by a receiver ofa first sensor device and from a transmitter of a second sensor device,a signal; determining a received signal strength indicator (RSSI) of thesignal; determining, by the first sensor device, a sensitivity level ofthe receiver; determining that the RSSI is greater than the sensitivitylevel; determining, in response to the determining that the RSSI isgreater than the sensitivity level and based on a difference between theRSSI and the sensitivity level, a transmission power level for thetransmitter of the second sensor device; and transmitting, to the secondsensor device, an indication of the transmission power level for thetransmitter of the second sensor device.
 2. The method of claim 1,wherein the indication comprises a request to reduce a power of thetransmitter to the transmission power level.
 3. The method of claim 1,wherein determining the received signal strength indicator comprisesdetermining a received signal strength per transmission packet.
 4. Themethod of claim 1, further comprising determining the sensitivity levelof a receiver of the second sensor device.
 5. The method of claim 1,wherein determining the transmission power level is further based atleast on absorption of the signal from the second sensor device.
 6. Themethod of claim 1, wherein transmitting the indication of thetransmission power level comprises transmitting, to the second sensordevice, a command to reduce a power of the transmitter of the secondsensor device.
 7. The method of claim 1, wherein transmitting theindication of the transmission power level comprises transmitting theindication of the transmission power level using a wirelesscommunication protocol.
 8. A system comprising: a first sensor devicecomprising a transmitter; and a second sensor device in communicationwith the first sensor device and comprising a receiver and a sensor,wherein the second sensor device is configured to: receive, by thesensor of the second sensor device and from the transmitter of the firstsensor device, a signal, determine a received signal strength indicator(RSSI) of the signal, determine that the RSSI is greater than asensitivity level of the receiver, determine, in response to determiningthat the RSSI is greater than the sensitivity level and based on adifference between the RSSI and the sensitivity level, a transmissionpower level for the transmitter of first sensor device, and cause, basedon the transmission power level, a power level of the first sensordevice to be modified.
 9. The system of claim 8, wherein the secondsensor device is configured to cause the power level of the transmitterof the first sensor device to be modified by reducing a transmissionpower of the transmitter.
 10. The system of claim 8, wherein the secondsensor device is configured to determine the received signal strengthindicator by determining a received signal strength per transmissionpacket.
 11. The system of claim 8, wherein the second sensor device isfurther configured to determine the sensitivity level of the receiver.12. The system of claim 11, wherein the second sensor device isconfigured to determine the sensitivity level based at least on gain ofan antenna of the second sensor device.
 13. The system of claim 8,wherein the second sensor device is configured to cause the power levelof the transmitter of the first sensor device to be modified bytransmitting, to the first sensor device, an indication of thetransmission power level.
 14. The system of claim 13, wherein the secondsensor device is configured to transmit the indication of thetransmission power level to the first sensor device using a wirelesscommunication protocol.
 15. A device comprising: one or more processors;and memory storing instructions that, when executed by the one or moreprocessors, cause the device to: determine a received signal strengthindicator (RSSI) of a signal received by a receiver and transmitted by atransmitter of a sensor device; determine that the RSSI is greater thana sensitivity level of the receiver; determine, in response to thedetermining that the RSSI is greater than the sensitivity level andbased on a difference between the RSSI and the sensitivity level, atransmission power level for the transmitter of the sensor device; andtransmit, to the sensor device, an indication of the transmission powerlevel for the transmitter of the sensor device.
 16. The device of claim15, wherein the indication of the transmission power level comprises arequest to reduce a power of the transmitter of the sensor device to thetransmission power level.
 17. The device of claim 15, wherein theinstructions that, when executed by the one or more processors, causethe device to determine the received signal strength indicator compriseinstructions that, when executed by the one or more processors, causethe device to determine a received signal strength per transmissionpacket.
 18. The device of claim 15, wherein the device further comprisesthe receiver.
 19. The device of claim 15, wherein the instructions, whenexecuted by the one or more processors, further cause the device todetermine the sensitivity level of the receiver.
 20. The device of claim15, wherein the instructions that, when executed by the one or moreprocessors, cause the device to transmit the indication of thetransmission power level comprise instructions that, when executed bythe one or more processors, cause the device to transmit, to the sensordevice, a command to reduce a power of the transmitter to thetransmission power level.